Three-dimensional measuring apparatus and three-dimensional measuring method

ABSTRACT

The invention provides a measuring apparatus that can efficiently analyze a three-dimensional image by simultaneously recording a circular streak image and a straight-line streak image at a measured point, even when a large number of circular streak images are present. A measuring apparatus includes: a 3CCD camera; a cubic beam splitter that combines optical images incident from plural routes; a mirror that shifts an image focusing position of an optical image at a measured point by a predetermined distance; a coloring unit that applies a predetermined color to an optical image incident to a route of the beam splitter; a motor that rotates the beam splitter and the mirror in a direction of an arrowhead; and a PC that calculates a three-dimensional position of the measured point based on the optical image recorded by a camera.

This application is a reissue of U.S. Pat. No. 7,499,184, Ser. No.11/400,269, filed Apr. 7, 2006, which is a continuation ofPCT/JP2003/016509, filed Dec. 22, 2003, that claims priority to Japanesepatent application number JP2003-354101, filed Oct. 14, 2003.

This application claims priority from Patent Cooperation TreatyApplication Number PCT/JP2003/016509, filed 22 Dec. 2003, which claimspriority from Japanese Patent Application number JP2003-354101, filed 14Oct. 2003.

TECHNICAL FIELD

The present invention relates to a three-dimensional measuringapparatus, and more particularly relates to a three-dimensionalmeasuring apparatus and a three-dimensional measuring method that makeit possible to carry out accurately a three-dimensional measurement ateach measuring point even when plural measured points overlap with oneanother.

BACKGROUND ART

Conventionally, a three-dimensional measuring method that uses theprinciple of a stereoview using plural CCD cameras is known. Accordingto the conventional technique, measuring points need to be matched amongimages recorded from different directions, and the processing of theseimages is complex and ambiguous.

FIG. 7 is a schematic configuration diagram of a three-dimensionalmeasuring apparatus that is devised to solve the above conventionalproblem. A three-dimensional measuring apparatus 100 rotates a rotatingcylinder 33 via a gear 31 that is rotated by a motor 30, therebyrotating mirrors 34 and 35 fitted to the front end of the rotatingcylinder 33. With this arrangement, a camera 32 records a circularstreak image 36 at a measured point 37. FIG. 8 is a schematicconfiguration diagram of a three-dimensional measuring apparatusaccording to another method. A three-dimensional measuring apparatus 200rotates a rotating cylinder 42 via a gear 41 using a motor (not shown),thereby rotating a reflector 43 fitted to the front end of the rotatingcylinder 42 with an angle. With this arrangement, a camera 40 records acircular streak image 45 of a measured point 44. By appropriately usingthe three-dimensional measuring apparatuses 100 and 200 according to adistance to a measuring point, a satisfactory three-dimensionalmeasurement can be carried out when the number of measuring points issmall and when the moving speed of the measuring points is slow. Thethree-dimensional measuring apparatus 100 is granted as Japanese PatentNo. 3346662.

However, when the moving speed of the measuring points is fast, a streakimage of the measuring points becomes spiral as shown in FIG. 9. In thisspiral moving streak, a size variation and a pitch of a spiral streakcorrespond to three-dimensional velocity information. When this relationcan be analyzed, three components of positions and three components ofvelocity can be obtained at the same time. However, according to theconventional apparatus, it is difficult to analyze overlapped streaks inthe case that the number of measuring points is large.

A circular streak can be approximately analyzed by rotating a system ata sufficiently faster speed than the moving speed of the measuringpoints. However, an accurate analysis of a spiral image withoutapproximation is desired.

In the light of the above problems, it is an object of the presentinvention to provide a three-dimensional measuring apparatus that canefficiently analyze a three-dimensional image by simultaneouslyrecording a circular streak image and a straight-line streak image at ameasured point, even when a large number of circular streak images arepresent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a configuration of main parts of athree-dimensional measuring apparatus according to an embodiment of thepresent invention;

FIG. 2 is a block diagram of a total configuration of thethree-dimensional measuring apparatus according to the invention;

FIG. 3 is a diagram of phases of a spiral corresponding to points on acenter line according to the invention;

FIG. 4 is a distribution diagram of a distance between a point on atarget straight-line streak Q and a point on a spiral streak Pcorresponding to the point on the streak Q (between points c and j incorresponding phase directions) according to the invention;

FIG. 5(a) is an explanatory diagram of a relation between a distance ofa measured point and a streak image;

FIG. 5(b) is an explanatory diagram of a relation between a mirrorposition and a streak image;

FIG. 6 is a diagram of an image of tracer particles in a fluid that isimaged by a test unit of the three-dimensional measuring apparatusaccording to the invention;

FIG. 7 is a schematic configuration diagram of a conventionalthree-dimensional measuring apparatus;

FIG. 8 is a schematic configuration diagram of a conventionalthree-dimensional measuring apparatus according to another method; and

FIG. 9 is a diagram showing that a streak image of measuring pointsbecomes a spiral streak.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained in detail below by way ofembodiments shown in the accompanying drawings. Note that theconstituent elements, kinds, combinations, shapes, and relativepositions according to the embodiments are not intended to limit therange of the present invention, unless otherwise specified. Theembodiments are used simply for the purpose of explanation.

FIG. 1 is a perspective view of a configuration of relevant parts of athree-dimensional measuring apparatus according to an embodiment of thepresent invention. A three-dimensional measuring apparatus 50 includes:a 3CCD camera (an imaging unit) configured by CCDs of three primarycolors (hereinafter, simply referred to as a camera) 11; a cubic beamsplitter (hereinafter, simply referred to as a beam splitter) 12 thatcombines optical images incident from plural routes; a mirror 14 thatshifts an image forming position of an optical image at a measured point18 by a predetermined distance; a red filter (a coloring unit) 13 thatapplies a predetermined color to an optical image incident to a route ofthe beam splitter 12; a motor (not shown) that rotates the beam splitter12 and the mirror 14 in a direction of an arrowhead 17; and a PC (notshown) that calculates a three-dimensional position of the measuredpoint 18 based on the optical image recorded by the camera 11. While thered filter 13 is used for the coloring unit, other colors can be alsoused. The rotation direction of the motor can be opposite to thedirection explained herein.

FIG. 2 is a block diagram of a total configuration of thethree-dimensional measuring apparatus according to the invention.Constituent elements that are the same as those in FIG. 1 are assignedwith like reference numerals, and a redundant explanation is omitted. Inthis configuration, the beam splitter 12 and the mirror 14 areintegrated into a rotating cylinder 62, and are rotated in the directionof the arrowhead 17 by a motor (a rotating unit) 61 around an opticalaxis 15 of the camera 11. A PC (a calculating unit) 60 detects the imagerecorded by the camera 11, and processes the image. The PC 60 alsocontrols a detection of the rotation angle of the motor 61.

The outline operation of the three-dimensional measuring apparatusaccording to the embodiment is explained below with reference to FIG. 2.The beam splitter 12 and the mirror 13 are integrated together, and arerotated at a high speed (for example, 3,600 r/min) around the opticalaxis 15 of the camera 11. A high-speed hollow-shaft pulse motor is usedto drive the integrated combination of the beam splitter 12 and themirror 13. The camera 11 is incorporated in the hollow part of thehollow-shaft pulse motor, thereby miniaturizing the system. Light 16that is reflected by the mirror 14 and is imaged and is shifted by theoptical axis 15. Therefore, this light forms a circular (spiral) streaklike the light formed by the conventional apparatus. Light 19 thatproceeds straight through the beam splitter 12 forms a point (a straightline) which shows the center of the circular streak. The light 19 thatproceeds straight through the beam splitter 12 passes through the colorfilter 13. The color camera 11 images this light so that the light canbe easily identified by its color. In other words, as shown in FIGS. 2and 3, the measured point 18 is imaged as a combination of a circular(spiral: when the movement is fast) streak P based on the circularshift, and a straight-line streak Q which shows a two-dimensionalposition (movement) . These two kinds of streaks can be easilyidentified by processing the images in color. A direction of thestraight-line streak Q that shows the center of the streak can beidentified based on a winding direction of the spiral streak P (asexplained in detail later).

When a pulse motor is used for the motor to analyze the spiral streak, arotation angle of the pulse motor is necessary at the starting point andthe ending point of the imaged streak. A counter is reset to zero at a Zphase of the pulse motor. Then, the counter counts the pulse. The PC 60reads the output of the counter when a vertical synchronization signalof the image signal is generated, thereby detecting a drawing startingposition (a direction) and a drawing ending position (a direction) ofthe spiral. The detected values become information to be used toautomatically analyze the spiral.

FIG. 3 is a diagram of phases of the spiral corresponding to points onthe center line. The direction of the straight-line streak Q showing thecenter of the streak can be identified based on the winding direction ofthe spiral streak. In other words, when the rotation direction of thebeam splitter 12 and the mirror 14 is the counterclockwise direction,the spiral streak on the recorded image becomes in the clockwiserotation. Therefore, it is clear that the measured point 18 shifts fromleft (a) to right (b) in FIG. 3. The PC 60 first recognizes thestraight-line streak Q that shows the center of the streak, based on alabeling processing, and measures a three-dimensional motion state ofthe measured point 18 based on the corresponding spiral streak P. Withina short time of one rotation of the apparatus, the measured point (atracer particle) 18 can be assumed as substantially a constant-speedmotion. Considering the fact that the apparatus also rotates at aconstant speed, phases of the spiral streak corresponding to respectiveintersecting points (c to j) on the straight-line streak Q showing thecenter can be determined as those shown in FIG. 3. In other words, whilea point on the straight-line streak Q showing the center in FIG. 3shifts from the point a to the point b, the point shifts in thedirection of 0, 1, 2, . . . , 7, and (8) on the spiral streak.

FIG. 4 is a distribution diagram of a distance between a point on thetarget straight-line streak Q and a point on the spiral streak Pcorresponding to the point on the streak Q (between the points c and jin corresponding phase directions) . The vertical axis represents adistance from the center line Q to the streak P, and the horizontal axisrepresents points on the center line Q. A streak to be extracted along atarget straight-line streak P becomes a straight line X in the graph. Astreak A and a streak B become an ellipse in the graph. Therefore, evenwhen many streaks are overlapped, a spiral can be effectively extracted,and the three-dimensional motion state can be analyzed. These processesare carried out for all labeled center points (a center straight line).

As explained above, since the three-dimensional measuring apparatus 50according to the present embodiment uses the beam splitter 12, it ispossible to simultaneously record the straight-line streak image Q (adirect image at the measured point 18) as well as the conventionalcircular streak image. Further, the color film 13 is fitted to thesurface of the beam splitter 12 to which the straight-line streak imageis incident, thereby coloring the incident optical image. Consequently,the circular streak image P and the straight-line streak image Q can beidentified separately by processing these images with the PC 60. Thethree-dimensional measuring apparatus further includes the PC 60 thatcalculates a three-dimensional position based on the circular streakimage P and the straight-line streak image Q recorded by the camera 11.

FIG. 5(a) is an explanatory diagram of a relation between a distance ofa measured point and a streak image. First, a relation between adistance of a measured point and a streak image when the measured pointmoves from a point 20 to a point 21 is explained. A mirror 29 reflectslight 26 from the measured point 20 to a beam splitter 23 at areflection angle β. The light is further reflected from the beamsplitter 23 to a light-receiving surface 25 of a camera 24 and forms animage at a point b. Light from an optical axis P passes through a colorfilter 22, reaches the light-receiving surface 25 of the camera 24, andforms an image at a point a. When the measured point moves to the point21, light 27 of the measured point 21 is reflected from the mirror 29 tothe beam splitter 23 at a reflection angle α. The light is furtherreflected from the beam splitter 23 to the light-receiving surface 25 ofthe camera 24, and forms an image at a point c. An important pointherein is that the reflection angles β and α have a relation of β>α, andtherefore, when a distance between the measured point and thelight-receiving surface 25 becomes long (when the measured point is thepoint 20), the shift amount becomes small. When a distance between themeasured point and the camera becomes short (when the measured point isthe point 21), the shift amount becomes large. As a result, when it isassumed that the measured point does not shift to left and rightdirections, a spiral streak is imaged around the point a as shown at theright lower side in FIG. 5(a).

FIG. 5(b) is an explanatory diagram of a relation between a mirrorposition and a streak image. Constituent elements that are the same asthose in FIG. 5(a) are assigned with like reference numerals. A relationbetween a mirror position and a streak image when the mirror moves froma position 29 to a position (29) is explained. The mirror 29 reflectsthe light 26 from the measured point 20 to the beam splitter 23 at thereflection angle β. The light is further reflected from the beamsplitter 23 to the light-receiving surface 25 of the camera 24 and formsan image at the point b. The light from the optical axis P passesthrough the color filter 22, reaches the light-receiving surface 25 ofthe camera 24, and forms an image at the point a. When the mirror shiftsto the position (29), the light 27 of the measured point 20 is reflectedfrom the mirror at the position (29) to the beam splitter 23 at thereflection angle α. The light is further reflected from the beamsplitter 23 to the light-receiving surface 25 of the camera 24, andforms an image at the point c. An important point herein is that thereflection angles β and α have a relation of β>α, and therefore, when adistance between the mirror and the beam splitter 23 becomes long (whenthe mirror is at the position (29)), the shift amount becomes large.When a distance between the mirror and the beam splitter 23 becomesshort (when the mirror is at the position 29), the shift amount becomessmall. As explained above, a shift amount of the image can be changed bychanging a distance between the mirror and the beam splitter. Therefore,a measurement can be achieved according to a distance of a target. Inother words, a shift amount of the image can be changed by changing adistance between the mirror 29 and the beam splitter 23. Therefore, ameasurement can be achieved according to a distance of the measuredpoint 20. For example, when the mirror 29 is fixed to the beam splitter23, the shift amount becomes small and a measurement becomes impossiblewhen the measured point becomes far. In this case, the shift amount canbe increased by increasing a distance between the mirror 29 and the beamsplitter 23, thereby making it possible to achieve a measurement.

FIG. 6 is a diagram of an image of tracer particles in a fluid that isimaged by a test unit of the three-dimensional measuring apparatusaccording to the invention. It is clear from this image that a centerpoint (a straight-line streak) and a circular streak of each tracerparticle can be clearly identified and that it is easy to identify eachstreak from overlapped streak images that are present at the center ofthe image.

According to the invention, by using the beam splitter, the conventionalcircular streak image and the colored straight-line streak image can berecorded in combination, thereby making it possible to specify manyoverlapped circular streak images.

According to the invention, since the imaging unit records the coloredstraight-line streak image and the circular streak image, a movingdistance and a direction of the measured point can be calculated fromthe straight-line streak image, and a distance from the circular streakimage to the measured point calculated.

According to the invention, a center of a circular streak image isobtained from a straight-line streak image recorded by the imaging unit,thereby extracting a circular streak image corresponding to the center.

According to the invention, since a distance between the mirror and thebeam splitter can be changed, a shift amount of the circular streakimage can be adjusted based on the distance of the measured point.

According to the invention, when the rotating unit is a pulse motor, thecalculating unit calculates a rotation angle of the pulse motor at thestarting point and the ending point of the circular streak image.

Therefore, a drawing starting position (a direction) and a drawingending position (a direction) of the spiral can be detected. Thedetected information can be used for the automatic analysis of thespiral.

The present invention provides a three-dimensional measuring apparatusthat carries out a three-dimensional measuring of a measured point, saidthree-dimensional measuring apparatus comprising: an imaging unit thatcan detect at least two kinds of colors; a beam splitter that combinesoptical images that are incident from a plurality of routes; a mirrorthat slides, an image forming position of an optical image at saidmeasured point by a predetermined distance; a coloring unit that appliesa predetermined color to an optical image incident to a route of saidbeam splitter; a rotating unit that rotates said beam splitter and saidmirror at a predetermined rotational velocity; and a calculating unitthat calculates a three-dimensional position of said measured pointbased on an optical image recorded by said imaging unit.

According to the present invention, a beam splitter is used to make itpossible to simultaneously record a straight-line streak image (a directimage at a measured point) and the conventional circular streak image.Further, a color film is fitted to a surface of the beam splitter towhich the straight-line streak image is incident, thereby coloring theincident optical image. Consequently, the circular streak image and thestraight-line streak image can be identified separately by processingthese images. The three-dimensional measuring Apparatus further includesa calculating unit that calculates a Three-dimensional position based onthe circular streak image and The straight-line streak image recorded bythe imaging unit.

According to the present invention, by using the beam splitter, theconventional circular streak image and the colored straight-line streakimage can be recorded in combination, it is possible to specify manyoverlapped circular streak images. Therefore, a three-dimensional imagecan be analyzed efficiently.

The invention provides the three-dimensional measuring apparatus,wherein said calculating unit obtains, from said imaging unit, astraight-line streak image at said measured point that has passedthrough said coloring unit and a circular streak image from said mirrorthat is rotated by said rotating unit, thereby calculating a movingdirection of said measured point and a distance to said measured point,and thereby measuring a three-dimensional position and a moving velocityof said measured point.

The imaging unit detects a colored straight-line streak image and acircular streak image. For example, a color camera having CCDs of threeprimary colors detects a colored straight-line streak image and acircular streak image at the measured point. The calculating unitdetects an image signal with a PC or the like, calculates a movingdistance and a direction of the measured point using the straight-linestreak image, and calculates a distance to the measured point using thecircular streak image. The calculating unit can obtain athree-dimensional position of the measured point from the result of thecalculations.

According to the present invention, since the imaging unit detects thecolored straight-line streak image and the circular streak image, thecalculating unit can calculate a moving distance and a direction of themeasured point from the straight-line streak image, and calculate adistance to the measured point from the circular streak image. Thecalculating unit can both obtain a three-dimensional position of themeasured point from the result of the calculation, and simultaneouslyidentify each measured point.

The invention provides the three-dimensional measuring apparatus,wherein said calculating unit obtains a center of said circular streakimage from said straight-line streak image recorded by said imagingunit, and extracts a circular streak image corresponding to said center,thereby making it possible to identify a specific circular streak imagefrom among a plurality of circular streak images.

When a large number of circular streak images are overlapped, in orderto identify each circular streak image, a center of a circular streakimage is recognized first by the color image processing, and a circularstreak image corresponding to the center is extracted. With thisarrangement, the analysis can be carried out efficiently, even when alarge number of circular streaks are present within an image.

According to the present invention, a center of a circular streak imageis obtained from a straight-line streak image recorded by the imagingunit, thereby extracting a circular streak image corresponding to thecenter. With this arrangement, the analysis can be carried outefficiently, even when a large number of circular streaks are presentwithin an image.

The invention provides the three-dimensional measuring apparatus,wherein a distance between said mirror and said beam splitter can bechanged to make it possible to adjust a shift amount of said circularstreak image.

Since the shift amount of an image can be changed by changing thedistance between the mirror and the beam splitter, a measuring can becarried out according to a distance of a target. For example, when themirror is fixed to the beam splitter, a shift amount becomes small whenthe measured point is far. This makes it impossible to carry out ameasuring. In this case, by increasing the distance between the mirrorand the beam splitter, the shift amount increases, and it becomespossible to carry out a measuring.

According to the present invention, since a distance between the mirrorand the beam splitter can be changed, a shift amount of the circularstreak image can be adjusted based on the distance of the measuredpoint.

The invention provides the three-dimensional measuring apparatus,wherein when said rotating unit is a pulse motor that rotates based on aphase difference of a pulse, said calculating unit calculates a rotationangle of said pulse motor at a starting point and an ending pointrespectively of said circular streak image, thereby detecting a positionat said starting point and a position at said ending point of saidcircular streak image.

In order to analyze a spiral streak, a rotation angle of the pulse motorat the starting point and the ending point of a streak to be imaged isnecessary. A counter is reset to zero at a Z phase of the pulse motor,and the counter counts the pulse. An output of the counter, when avertical synchronization signal of an image signal is generated, is readinto a personal computer. With this arrangement, a drawing startingposition (a direction) and a drawing ending position (a direction) ofthe spiral can be detected. The detected information can be used for theautomatic analysis of the spiral.

According to the present invention, when the rotating unit is a pulsemotor, the calculating unit calculates a rotation angle of the pulsemotor at the starting point and the ending point of the circular streakimage. Therefore, a drawing starting position (a direction) and adrawing ending position (a direction) of the spiral can be detected. Thedetected information can be used for the automatic analysis of thespiral.

1. A measuring apparatus that carries out a three-dimensional measuringof a measured point, the measuring apparatus comprising: an imaging unitthat can detect at least two colors; a beam splitter that combines atleast two optical images that are incident from a plurality of routes; amoveable mirror that shifts an image forming position of an opticalimage at the measured point by a predetermined distance; a coloring unitthat applies a predetermined color to an optical image incident to aroute of the beam splitter; a rotating unit that rotates the beamsplitter and the mirror at a predetermined rotational velocity; and acalculating unit that calculates a three-dimensional position of themeasured point based on an optical image recorded by the imaging unit.2. The measuring apparatus according to claim 1, wherein the calculatingunit obtains, from the imaging unit, a straight-line streak image at themeasured point that has passed through the coloring unit and a circularstreak image from the mirror that is rotated by the rotating unit,thereby calculating a moving direction of the measured point and adistance to the measured point, and thereby measuring athree-dimensional position and a moving velocity of the measured point.3. The measuring apparatus according to claim 2, wherein the calculatingunit obtains a center of the circular streak image from thestraight-line streak image recorded by the imaging unit, and extracts acircular streak image corresponding to a center, thereby making itpossible to identify a specific circular streak image from among aplurality of circular streak images.
 4. The measuring apparatusaccording to claim 1, wherein a distance between the mirror and the beamsplitter can be changed to make it possible to adjust a shift amount ofa circular streak image.
 5. The measuring apparatus according to claim1, wherein when the rotating unit is a pulse motor that rotates based ona phase difference of a pulse, the calculating unit calculates arotation angle of the pulse motor at a starting point and an endingpoint respectively of a circular streak image, thereby detecting aposition at the starting point and a position at the ending point of thecircular streak image.